What is Symmetric-Key cryptography and Asymmetric-Key cryptography?Symmetric-Key Cryptography: Symmetric-key cryptography uses a single key for both encryption and decryption. Encryption and decryption algorithm are inverse of each other.
To create the ciphertext from the plaintext John uses an encryption algorithm and a key. To create the plaintext from ciphertext, Bob uses the decryption algorithm and the same key.
Asymmetric-Key cryptography: It is also called public key cryptography. In public key cryptography two keys: a private key and a public key is used. Encryption is done through the public key and decryption through private key. Receiver creates both the keys and is responsible for distributing its public key to the communication community.
The sender (say John) uses the public key to encrypt the plaintext into ciphertext and the receiver (say Bob) uses his private key to decrypt the ciphertext.